Optical imaging of targets embedded in a highly scattering turbid medium, such as, a tumor in a breast, is a challenging problem because light is strongly absorbed and scattered by the medium leading to poor signal-to-noise ratio, as well as, loss of phase coherence and polarization. As a consequence distinct, sharp image of the targets may not be formed directly. Various frequency-domain, time-resolved, and steady-state inverse image reconstruction (IIR) approaches are being pursued to form tomographic images using diffusively scattered light measured at the sample boundary. IIR is an ill-posed problem and the development of reliable and fast approaches remains a formidable task. Recent IIR algorithms, such as Newton-Raphson-Marquardt algorithms and direct linear inversion of 3-D matrices, are time consuming. The iterative methods may not ensure that the obtained result arrives at a “global minimum” or converges to a “local minimum.” Still the potential for developing non-invasive imaging approaches with diagnostic ability motivates the ongoing diffuse optical tomography (DOT) research using NIR light.
Many applications require rather accurate determination of location of target(s) in three dimensions. For example, a recent study involving 35,319 patients underscores the influence of primary tumor location on breast cancer prognosis, and makes it imperative that DOT for breast cancer detection be able to obtain three-dimensional (3-D) location of the tumor. While two-dimensional (2-D) IIR approaches may provide only lateral positions, 3-D IIR approaches attempt to retrieve all three position coordinates of the target(s). Various frequency-domain, time-domain, and steady-state DOT approaches have addressed the target localization problem with different measures of success.
The discussion above is merely provided for general background information and is not intended to be used as an aid in determining the scope of the claimed subject matter.